While, for clarity, the present process will be described in relation to a drum or substrate useful in ink jet technology, it should be understood that this process can be used to produce any substrate where supplying of drum maintenance fluid and coalescing of liquids in contact therewith is a concern. The present process and method can be described in relation to a fusing surface or any surface that requires the application of a thin film of release fluid.
Ink jet printers are known which comprise: an ink source, a printing head connected to the ink source for projecting droplets of ink under the control of electrical input signals representative of information to be printed, a printing medium e.g., a sheet or strip of paper located in the paths of the projected ink droplets and an arrangement for providing relative motion between the printing head and the printing medium. While such printers have enjoyed substantial commercial success, they are not without several inherent difficulties. For example, known ink jet printers tend to produce inconsistent printed copies. Ink jet printing systems have been employed in the prior art such as those disclosed in U.S. Pat. Nos. 4,538,156; 4,731,647; 4,833,530; 5,099,256, 6,899,419; 6,923,533, and 7,014,897. All of these patents are incorporated by reference into the present disclosure.
Generally, in ink jet printing, liquid is supplied from a solvent supply source to a recording head which is responsive to a modulation signal from a control circuit to apply an ink droplet to a drum or writing surface. Generally, an intermediate transfer surface is used which is a liquid layer that is applied to a drum but may also be a web, platen or any other suitable receiving surface. The drum can comprise a metal such as aluminum, nickel or iron phosphate or mixtures thereof coated with elastomers such as Viton or Teflon (trademarks of dupont), Tecnoflon P59 (a trademark of Dow). Fluoroelastomers, perfluoroelastomers, silicone rubber and polybutadiene, plastics including but not limited to polytetrafluorethylene loaded with polyphenylene sulfide, thermoplastics such as polyethylene, nylon and FEP, thermosets such as acetals, or ceramics could be employed as long as the exposed surface is sufficiently rigid to deform the transferred image-forming ink when the final receiving medium passes between it and the transfer and fixing roller and sufficiently smooth so as not to interfere with the ability of the intermediate transfer surface or liquid layer to support the image-forming ink. The preferred drum material is anodized aluminum and a preferred elastomer is Viton®.
The imaging drum for future high-speed piezo ink jet printers comprises this noted compliant fluoroelastomer coating over an aluminum core. The surface texture of such a coating is an important consideration to enable pinning of individual ink droplets for high quality imaging. Smooth, low surface energy, low thermal conductivity surfaces create conditions that allow ink droplets the energy and time to move and coalesce on the surface of the drum. This phenomenon has been referred to as ink drawback and is more pronounced at high temperature. It reduces image quality and manifests itself as areas void of ink or mottled areas in the final image. For example, a continuous line of a given width may print as a randomly broken line of varying width or a solid area may print with an objectionable level of random areas void of ink.
This invention is an innovative method for texturing the surface of compliant coatings such as fluoroeslastomers of Viton GF and Tecnoflon P959 on aluminum piezo ink jet print drums to a specific pre-determined texture in order to prevent ink drawback and maintain image quality. Smooth, low energy, homogeneous surfaces inhibit droplet pinning and lead to drawback or a coalescence of individual ink droplets on the compliant surface. This phenomenon reduces image quality and manifests itself as areas void of ink of mottled areas in the final image. For example, a continuous line of a given width may print as a randomly broken line of varying width or a sole area may print with an objectionable level of random areas void of ink.
Examples of bases include magnesium oxide (MgO), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), potassium carbonate (K2CO3) and the like. Etching of the drum surface with an acid such as acetic acid will lead to a reaction to form a water-soluble salt of the particular base and water which can then be removed by washing the drum in water.MgO+2CH3COOH→(CH3COO)2Mg+H20.